JPS6381289A - Distance measuring equipment - Google Patents

Abstract

PURPOSE:To reduce errors in measurement and to improve the measurement accuracy of the distance to a body by providing a correcting means which corrects a time difference or distance according to the reception level of electromagnetic pulses. CONSTITUTION:A detector 21 detects a received pulse (c) amplified by a wide- band amplifier 9 and outputs a DC voltage VS corresponding to a reception level. A level discriminating circuit 22 discriminate the outputted voltage VS by a comparator array to decide which level range the reception level is in. Further, an arithmetic part 23 determines and corrects a correction coefficient stepwise according to the output of the circuit 22. Consequently, an arithmetic part 23 measures the pulse width of the output (e) of a RF.FF 12, reads the output of the comparator whose reference voltages is lowest, and reads a time correction coefficient corresponding to the reception level out of a memory. Then, the distance is calculated from the coefficient and pulse width. Therefore, the error in measurement becomes smaller than when no correction is made, and distance correction corresponding to the reception level is performed, so that the measurement accuracy of the distance is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a distance measuring device that uses electromagnetic pulses to measure the distance between an electromagnetic pulse transmitter/receiver and an object, and in particular to a distance measuring device that uses electromagnetic pulses to measure the distance between an electromagnetic pulse transmitter/receiver and an object, and in particular to a distance measuring device that uses electromagnetic pulses to measure the distance between an electromagnetic pulse transmitter/receiver and an object. Concerning distance devices.

BACKGROUND OF THE INVENTION A vehicle-mounted distance measuring device is used to measure the distance to an object by transmitting electromagnetic pulses and processing the received pulses reflected by an object in front of the vehicle. Conventionally, as shown in FIG. 5, a transmitting section 1, a receiving section 6, and a processing section 10 constitute a distance measuring device, and the transmitting section 1 includes a pulse drive circuit 2, an electromagnetic wave generating means, for example, a laser diomide 3, It consists of a transmitting lens 4. The receiving section 6 includes a receiving lens 7, a photoelectric conversion element 8 that converts light from the receiving lens 7 into an electrical signal, and a broadband amplifier 9 that amplifies the output thereof. Further, the processing section 10 includes a high-speed comparator 1 that receives the output pulses from the pulse drive circuit 2 and shapes the pulses according to the threshold level.
1 and a high-speed comparator 12 that receives the output pulses of the broadband amplifier 9 and shapes the pulses according to the threshold level;
R-S that shapes a pulse according to the time difference between these two pulses
It consists of a flip-flop 13 and an arithmetic unit 14 that converts this pulse width into distance.

Next, signals and pulse shaping will be explained with reference to the signal time chart in FIG.

The transmission pulse is shaped into a pulse (al is fb according to the threshold level 15 of the high-speed comparator 11) and R
-S is added to the S terminal of the flip-flop 13. Further, the received pulse (C) amplified by the broadband amplifier 9 is determined by the threshold level 16 of the high-speed comparator 12 (d
) is shaped into a pulse signal and applied to the R terminal of the R-S flip-flop 13. Using the falling edges of these two pulses, a signal (e) with a pulse width T is applied to the arithmetic unit 14 by the R/S flip-flop 13. This time T is
It represents the time from transmission to reception of the transmission pulse, and has a relationship with the distance MR to the object as shown in equation (1).

Therefore, by measuring the pulse width T in the calculation section 14, the distance R can be determined.

Problems to be Solved by the Invention However, in the conventional measuring device described above, the level of the transmitted pulse (al) does not change, but the level of the received pulse (C) changes depending on the distance R to the object or the shape of the object 5, etc. As shown in Fig. 7, a measurement error of △T occurs depending on the amplitude of the received pulse (C1).As shown in Fig. 7, a measurement error of △T occurs depending on the strength of the reception level. A measurement error △T as shown in the relationship diagram occurs,
There was a problem that caused a distance error.

The present invention was made in view of such problems, and an object of the present invention is to reduce measurement errors and improve accuracy in measuring distances to objects.

Means for Solving the Problems In order to achieve the above object, the present invention transmits an electromagnetic wave pulse and receives the electromagnetic wave pulse reflected by an object,
A distance measuring device that measures the distance between an electromagnetic pulse transmitting/receiving unit and the object based on the time difference between the transmitted pulse and the received pulse, further comprising a correction means for correcting the time difference or distance according to the reception level of the electromagnetic pulse. This is a distance measuring device characterized by:

The smaller or larger the effect reception level is, the larger the distance measurement error becomes. Therefore, according to the present invention, the reception level is detected and the time difference between the transmission pulse and the reception pulse or the distance to the object is corrected according to its magnitude, so that the accuracy of measuring the distance can be improved.

Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, the same parts as in FIG. 5 are given the same reference numerals.

As shown in the figure, 21 is a detector, and a broadband amplifier 9
The received pulse (C1) amplified by is detected and extracted as a DC voltage Vs according to the received level. 22 is a level discrimination circuit, which discriminates the detected output Vs by a plurality of comparator arrays and determines in which level range the received level falls. Determine if there is.2
3 is an arithmetic unit which determines a correction coefficient according to the output signal of the level discrimination circuit 22 and performs correction in stages. .

FIG. 2 is a block diagram showing a specific example of the level discrimination circuit 22.

The detection output Vs is generated by a plurality of comparator arrays COMh, C
OMPz,----COMP, is added to one terminal,
Each child terminal has a resistor R,, R2-・-・-・R, l,
The reference voltage vrstz, V F@ defined by R,
ft5-・-・-= V p@(6(V r*fl <
V 1@f2 <----V y@yJ is added.

Therefore, the comparator string GOMP coMpz ・−
...The reception level can be determined by the output of COMP and %.

The operation of this embodiment will be explained below with reference to FIG. Fourth
The figure is a flowchart showing the processing in the calculation unit 23. High-speed comparator 11.12 and R-S flip-flop 13 in the transmitter 1, receiver 6 and processor 10
Since the operation is the same as that in FIG. 5, the explanation here will be omitted. The calculation unit 23 measures the pulse width T of the output (e) of the R-S flip-flop 13 (see FIG. 6(e)) in step S1, and then sets i=1 in step S2.
Then, the process moves to step S3. Steps S3 and S4 are steps in which the reception level is determined based on the comparator array COMP1 to COMP, and the outputs of the comparators COMP1 with the lowest reference voltage Vrat are read sequentially. In step S3, for example, if the output of the comparator COMP:l is "1" when i=3, the reception level "5" is Vr*f2, Vs ≦V re,
It turns out that it is 3. In step S5, the time correction coefficient Ti corresponding to the reception level v3 is read from the memory.

As shown in FIG. 3, this time correction coefficient Ti is set to a larger value as the reception level becomes smaller or larger. In step S6, the distance R is calculated based on the time correction coefficient Ti and the pulse width T obtained in step Sl, and in step S
Output at 7. Therefore, the relationship between the reception level and the measurement error after correction is as shown in FIG. 3, and the measurement error is much smaller than when no correction is performed. In this way, distance correction can be performed according to the reception level, and distance measurement accuracy is improved.

In the above embodiment, the distance R was corrected by correcting the pulse width T according to the reception level, but the distance R was corrected according to the reception level.
The IR may be directly corrected. The calculation formula in this case is -CR=-+C,i, where Ci is a distance correction coefficient depending on the reception level. As another embodiment, as shown by the dashed line in FIG. 1, the detected output V is AD converted by an AD converter 31, and the calculation section is programmed to function as a comparator array. A similar effect can also be obtained.

Effects of the Invention As described above in detail, according to the present invention, highly accurate distance measurement can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an embodiment of the level discrimination circuit 22, FIG. 3 is an error correction state diagram, FIG. 4 is a processing flowchart of the calculation unit 23, and FIG. 5 is a conventional block diagram, Figure 6 is a signal time chart, and Figure 7 is a conventional block diagram.
The figure is a diagram of causes of error occurrence, and FIG. 8 is a diagram of the relationship between reception level and measurement error. In the figure, 1 is a transmitting section, 2 is a pulse drive circuit, 3 is a laser diode, 4 is a transmitting lens, 5 is an object, 6 is a receiving section, 7 is a receiving lens, 8 is a photoelectric conversion element, 9 is a broadband amplifier, 10 is a processing unit, 11.12 is a high-speed comparator,
13 is an R-S flip-flop, 14 is an arithmetic unit, 21 is a wave detector, 22 is a level discrimination circuit, 23 is an arithmetic unit, Vs is a detection output, ■ is a DC voltage, 00MP+1COMF!
------COMP- is a comparator string, 31 is AD
It is a converter.

Claims (1)

[Claims] In a distance measuring device that transmits an electromagnetic pulse, receives the electromagnetic pulse reflected by an object, and measures the distance between the electromagnetic pulse transmitter/receiver and the object based on the time difference between the transmitted pulse and the received pulse. A distance measuring device comprising a correction means for correcting the time difference or distance according to a reception level.